Official national forms vary from country to country:
American: forearm at 45° angle to the forehead, blade hand with palm towards face.
British: similar to American, but with palm facing outward.
Straight-arm salute (also called Roman, Hitler or Nazi salute and was used by fascist or Nazi movements and governments, most notably Nazi Germany): straight arm extended forward and upwards.
Stylized forms appear in many magical girl titles:
Sailor Moon in particular popularized the "V" hand held sideways, partially framing the eye. This was later inherited by Asamiya Athena from KOF 96 onwards